Stenotic segments in the vessels and arteries of a patient can develop for many different reasons and can have different adverse effects on the patient. Depending on the location of the particular stenosis, the patient can experience cardiac arrest, stroke, or tissue and organ necrosis. Further, the severity of damage to the patient will, at least to some extent, depend on the nature of the stenosis and the extent of its development. Suffice it to say, stenotic segments can develop throughout a patient's cardio-vascular system, and can vary in size, shape and composition. Consequently, they vary in the degree to which they occlude blood flow through the vessel.
A stenosis in a vessel can be quite extensive and occlude a substantial length of a vessel. On the other hand, some stenoses are quite short. Further, some stenoses are highly calcified while other are not. The consequence is that, depending on the nature of the particular stenosis, some surgical tools and procedures are more appropriate than are others for clearing the stenosis.
Angioplasty is one of several types of medical procedures which has been widely used in recent years to surgically clear a stenosis in a vessel. More specifically, in an angioplasty procedure, a balloon is placed across the stenosis where it is inflated to dilate the stenosis.
Atherectomy is another type of medical procedure which, as an alternative to angioplasty, has been an acceptable and widely used procedure for surgically clearing a stenosis from a vessel. Quite unlike an angioplasty procedure, however, an atherectomy procedure results in the clearing of the vessel by cutting and removing the stenotic plaque from the vessel.
Still another type medical procedure, though somewhat like angioplasty in its effect on the stenosis, is a dilatation probe. For a procedure using a dilatation probe, the stenosis is simply approached by the probe and the probe is then pushed or urged through the stenosis. In an aggressive procedure, the probe can be moved back and forth through the stenosis. In any event, due to the dilating or spreading effect of the probe, the stenosis can be cleared. Further, in comparison with either an angioplasty or an atherectomy procedure, the use of a dilatation probe is relatively simple.
It has been determined that the dilatation of a stenosis is greatly facilitated if the stenosis is incised before the dilatation. Consequently, several devices have been proposed for this purpose. For example, U.S. Pat. No. 4,273,128 which issued to Lary for and invention entitled "Coronary Cutting and Dilating Instrument" discloses a serial combination of a distal longitudinal incisor and a proximal dilatation balloon. Further, U.S. Pat. No. 5,320,634 which issued to Vigil et al. for an invention entitled "Balloon Catheter with Seated Cutting Edges" discloses a device in which the incising blades are carried on the surface of the angioplasty balloon. Both of these patents are assigned to the same assignee as the present invention.
There is, of course, an ever present danger when sharp instruments are inserted into and through a vessel of a patient to incise tissue. Very importantly, the incising instrument, i.e. a sharpened blade, needs to be effectively covered during its insertion into the vessel in order to protect the vessel from inadvertent incisions. Such protection becomes increasingly more important as the distance for travel of the incising instrument through the vessel increases.
In light of the above, it is an object of the present invention to provide a universal incisor/dilator surgical tool which can selectively extend blades from the tool for incision of a stenotic segment. Another object of the present invention is to provide a universal incisor/dilator surgical tool which keeps its incising blades covered, to protect against inadvertent incision of the vessel wall, during transit of the tool through an artery or vessel to the stenosis. Yet another object of the present invention is to provide a surgical tool which can act simply as a dilator or, alternatively, as an incisor. Still another object of the present invention is to provide a universal incisor/dilator surgical tool which is relatively easy to manufacture, is simple to operate and is comparatively cost effective.